JP2016010746A - Crosslinked chitosan derivative-containing adsorptive material as well as method for adsorbing and method for recovering metallic ions - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adsorptive material that can separate and recover metallic ions, in particular indium ions and/or gallium ions, as well as to provide a manufacturing method of said adsorptive material, and a method for adsorbing and a method for recovering metallic ions by using said adsorptive material.SOLUTION: Provided is an adsorptive material comprising a crosslinked chitosan derivative containing a structural unit represented by the formula (I).

Description

  The present invention relates to an adsorbent containing a cross-linked chitosan derivative into which citric acid has been introduced, a method for producing the cross-linked chitosan derivative, and a metal ion adsorption method and recovery method using the adsorbent.

  Rare metals such as indium and gallium are widely used in electronic devices such as mobile phones, liquid crystal televisions, personal computers, and parts such as batteries. With recent rises in metal resource prices, metal resources are being recycled on an industrial scale.

  Indium is a raw material of a transparent conductive film (ITO, Indium Tin Oxide) used as a transparent electrode in flat panel displays such as liquid crystal and plasma and solar cells. As the demand for transparent conductive films increases, the price of indium is rising. Although attempts have been made to recycle indium, for example, etching waste liquid used in flat panel display manufacturing, and recovery of indium from waste electronic materials and waste electronic equipment such as waste flat panel displays used by consumers Due to cost and time, there is a need for a simple and efficient recovery method.

  Gallium is utilized as a compound semiconductor with elements such as phosphorus and arsenic in light emitting diodes, integrated circuits, solar cells, and the like, taking advantage of its light emission characteristics, high frequency characteristics, and the like. However, since recovery of gallium from waste electronic materials and waste electronic equipment requires cost and time, a simple and efficient recovery method is required.

  Indium and gallium are contained in, for example, smoke ash and residues, which are by-products in zinc refining and lead refining, and are industrially produced by separation and recovery from these. This separation is currently performed by adding zinc or aluminum metal powder to replace and deposit indium and gallium. However, this separation method consists of complicated processes and has low selectivity for indium and gallium. Therefore, much time and process are required to obtain high purity indium and gallium.

  Adsorbents using chitosan derivatives have been proposed as methods for recovering metal ions. For example, as an adsorbent that selectively adsorbs indium ions and gallium ions, an adsorbent containing a crosslinked chitosan derivative containing a phenylphosphinic acid group has been proposed (Patent Document 1). However, the adsorbent described in Patent Document 1 does not have sufficient adsorption characteristics for indium and gallium, for example, a sufficiently high saturated adsorption amount. Further, the crosslinked chitosan derivative containing a phenylphosphinic acid group described in Patent Document 1 has a complicated manufacturing process and further contains a phosphorus element, and thus cannot be said to be an environmentally friendly adsorbent.

  As another example of an adsorbent using a chitosan derivative, for example, an adsorbent obtained by reacting porous chitosan fine particles, hydroxyquinoline and aldehyde (Patent Document 2), an adsorbent containing crosslinked chitosan (Patent Document 3), An adsorbent containing a cross-linked chitosan derivative containing a pyridine ring (Patent Document 4) and the like can be mentioned. However, any of the adsorbents disclosed in these documents requires a complicated process for producing a chitosan derivative or does not have sufficient adsorption characteristics particularly for metal ions such as indium and gallium.

JP 2010-179205 A JP 2014-4518 A JP 2010-260028 A JP 2007-224333 A

  An object of the present invention is to provide an adsorbent capable of separating and recovering metal ions, particularly indium ions and / or gallium ions. Another object of the present invention is to provide a method for producing the adsorbent, and a method for adsorbing and recovering metal ions using the adsorbent.

  In order to solve the above-mentioned problems, the present inventors have studied the adsorbent and its production method in detail, and have completed the present invention.

で表される構造単位を含有する架橋キトサン誘導体を含む、吸着材。
〔２〕金属イオンを吸着するための吸着材であって、該金属イオンはインジウムイオンおよびガリウムイオンからなる群から選択される少なくとも１種である、前記〔１〕に記載の吸着材。
〔３〕キトサンとクエン酸とを混合し加熱下に脱水反応を行うことにより、架橋および官能基の導入を同時に行う、上記式（Ｉ）で表される構造単位を含有する架橋キトサン誘導体の製造方法。
〔４〕少なくとも１種の金属イオンを含有する溶液と、前記〔１〕または〔２〕に記載の吸着材とを接触させる工程を含む、金属イオンの吸着方法。
〔５〕少なくとも１種の金属イオンを含有する溶液と、前記〔１〕または〔２〕に記載の吸着材とを接触させる工程；および
前記工程で得た金属イオンが吸着された吸着材と、酸性溶液または塩基性溶液とを接触させて、該吸着材から該金属イオンを脱離させる工程；
を含む、金属イオンの回収方法。
〔６〕インジウムイオンおよびガリウムイオンを含有する溶液と、前記〔１〕または〔２〕に記載の吸着材とを接触させる工程；
前記工程で得たインジウムイオンおよびガリウムイオンが吸着された吸着材と、塩基性溶液とを接触させて、該吸着材からガリウムイオンを脱離させる工程；および前記吸着材と、酸性溶液とを接触させて、該吸着材からインジウムイオンを脱離させる工程を含む、前記〔５〕に記載の回収方法。 That is, the present invention includes the following preferred embodiments.
[1] Formula (I):

An adsorbent comprising a crosslinked chitosan derivative containing a structural unit represented by:
[2] The adsorbent for adsorbing metal ions, wherein the metal ions are at least one selected from the group consisting of indium ions and gallium ions.
[3] Production of a crosslinked chitosan derivative containing a structural unit represented by the above formula (I) in which chitosan and citric acid are mixed and subjected to a dehydration reaction under heating to simultaneously perform crosslinking and introduction of a functional group Method.
[4] A method for adsorbing metal ions, comprising a step of bringing a solution containing at least one metal ion into contact with the adsorbent according to [1] or [2].
[5] A step of bringing a solution containing at least one metal ion into contact with the adsorbent according to [1] or [2]; and an adsorbent on which the metal ion obtained in the step is adsorbed; Contacting the acidic solution or basic solution to desorb the metal ions from the adsorbent;
A method for recovering metal ions.
[6] A step of bringing a solution containing indium ions and gallium ions into contact with the adsorbent according to [1] or [2];
Contacting the adsorbent adsorbed with indium ions and gallium ions obtained in the step with a basic solution to desorb gallium ions from the adsorbent; and contacting the adsorbent with an acidic solution The recovery method according to [5], further including a step of desorbing indium ions from the adsorbent.

  According to the adsorbent of the present invention, metal ions, particularly indium ions and / or gallium ions, can be selectively adsorbed, separated and recovered.

It is the figure which showed the relationship between the adsorption rate of the metal ion to the adsorbent of this invention, and pH. It is the figure which showed the relationship between the adsorption rate of the metal ion to the adsorbent of the comparative example 1 which is not based on this invention, and pH. It is the figure which showed the relationship between the adsorption rate of the metal ion to the adsorbent of this invention, and pH.

で表される構造単位を含有する架橋キトサン誘導体を含む。 The adsorbent of the present invention has the following formula (I):

A crosslinked chitosan derivative containing a structural unit represented by:

  The cross-linked chitosan derivative preferably contains 50% or more of the structural unit represented by the above formula (I) based on the number of all glucosamine units constituting the cross-linked chitosan derivative, from the viewpoint of enhancing the adsorptivity of metal ions and the like. 80% or more is more preferable. The all glucosamine units constituting the crosslinked chitosan derivative may be structural units represented by the above formula (I).

The crosslinked chitosan derivative containing the structural unit represented by the formula (I) is a crosslinked chitosan derivative. Cross-linking is performed by at least one of a CH ₂ OH group at the 5-position in one glucosamine unit, an OH group at the 3-position, and an amino group at 2-position, and a CH ₂ OH group at the 5-position and an OH group at the 3-position in another glucosamine unit. And at least one of the amino groups at the 2-position are formed by dehydration condensation. The degree of cross-linking is not particularly limited, but is preferably 0.3 to 0.8, more preferably 0.5 to 0.8, from the viewpoint of appropriate swelling and usability. The degree of crosslinking can be measured by elemental analysis and weight change.

  The crosslinked chitosan derivative containing the structural unit represented by the formula (I) is not particularly limited. For example, it is derived from chitosan obtained by deacetylating chitin obtained from crustacean shells such as shrimp and crab. Well, it may be derived from commercially available chitosan. The degree of deacetylation of the crosslinked chitosan derivative is preferably 50% or more and more preferably 80% or more from the viewpoint of adsorption performance of metal ions and the like.

  The crosslinked chitosan derivative containing the structural unit represented by the formula (I) includes, for example, metal ions such as indium, gallium, lead, cobalt, zinc, manganese and magnesium, physiologically active substances such as amino acids, proteins and peptides, and Basic substances such as amines and ammonia can be adsorbed. The adsorbent of the present invention containing the crosslinked chitosan derivative is preferably an adsorbent for adsorbing metal ions, more preferably at least one selected from the group consisting of indium, gallium, zinc, copper and selenium. An adsorbent for selectively adsorbing metal ions, more preferably an adsorbent for selectively adsorbing at least one metal ion selected from the group consisting of indium, gallium and zinc, Preferably, it is an adsorbent for selectively adsorbing at least one metal ion selected from the group consisting of indium and gallium. Since the adsorbent of the present invention is usually solid and stable, it is suitable for industrial long-term use.

  The crosslinked chitosan derivative containing the structural unit represented by the above formula (I) is manufactured by mixing chitosan and citric acid and performing a dehydration reaction under heating, thereby simultaneously performing crosslinking and introduction of a functional group. Can do. The present invention relates to a crosslinked chitosan derivative containing a structural unit represented by the above formula (I), wherein chitosan and citric acid are mixed and subjected to a dehydration reaction under heating to simultaneously perform crosslinking and introduction of a functional group. A manufacturing method is provided. According to the production method of the present invention, a crosslinked chitosan derivative containing the structural unit represented by the above formula (I) can be easily produced in one step.

  Although it does not specifically limit as chitosan used with the manufacturing method of this invention, For example, chitosan obtained by deacetylating chitin obtained from crustacean shells, such as a shrimp and a crab, or commercially available chitosan is mentioned. The degree of deacetylation of chitosan is preferably 50% or more, and more preferably 80% or more, from the viewpoint of adsorption performance of metal ions and the like.

  In the production method of the present invention, the method for mixing chitosan and citric acid is not particularly limited. For example, an aqueous citric acid solution may be added to and mixed with solid chitosan. The mixing ratio of chitosan and citric acid is not particularly limited. For example, from the viewpoint of adsorption performance of metal ions and the like, the molar ratio of chitosan: citric acid is preferably 1: 1 to 1: 5, more preferably 1: 2 to 2. You may mix by the mixing ratio which will be 1: 5.

  In the production method of the present invention, the heating temperature when the dehydration reaction is performed under heating is usually 80 to 120 ° C, preferably 90 to 120 ° C, more preferably 100 to 120 ° C. The heating time may be appropriately selected according to the heating temperature, but is usually 1 to 3 hours, preferably 1.5 to 2 hours. From the viewpoint of easily producing a crosslinked chitosan derivative containing the structural unit represented by the above formula (I) by promoting the dehydration reaction, it is preferable to perform drying in the production method of the present invention. Drying may be performed by, for example, vacuum drying. Drying may be performed while heating, or heating and drying may be performed separately.

  The present invention further includes a step of bringing a solution containing at least one metal ion into contact with the adsorbent of the present invention containing a crosslinked chitosan derivative containing a structural unit represented by the above formula (I). A method for adsorbing metal ions is provided. By bringing the solution containing at least one metal ion into contact with the adsorbent of the present invention, the metal ions in the solution are adsorbed on the adsorbent.

  In the adsorption method of the present invention, the method of bringing the solution containing at least one metal ion into contact with the adsorbent of the present invention is not particularly limited. For example, (1) the present invention is applied to a solution containing metal ions. (2) Method of filling the column with the adsorbent of the present invention and passing a solution containing metal ions from one end of the column (batch method) Any one or both of column methods); When the amount of the solution to be treated is small, it is preferable to use the column method because a high adsorption rate can be easily achieved. When the amount of the solution to be treated is large, it is preferable to use a batch method from the viewpoint of reducing cost and labor.

  When the solution containing metal ions and the adsorbent of the present invention are brought into contact with each other by a batch method, mixing may be performed by a stirring device installed in the container, and the entire container is shaken by a shaking device installed outside the container. Mixing may be carried out by this. The stirring speed and the shaking speed may vary depending on the shape of the container used and the volume of the solution, but the stirring speed is usually about 100 to 200 rpm, and the shaking speed is usually about 100 to 200 rpm. The time required for the adsorption of metal ions to the adsorbent to reach an equilibrium state may vary depending on the type and concentration of the target metal ions, but is usually 2 to 12 hours. Moreover, the temperature until reaching an equilibrium state is usually 20 to 30 ° C.

In the adsorption method of the present invention, as the solution containing at least one kind of metal ions, for example, a solution containing metal ions such as a waste liquid may be used as it is, or an appropriate pretreatment is performed to obtain an insoluble residue or target. A solution excluding various impurities other than metal ions may be used. The concentration of the target metal ion in the solution is preferably 0.1 to 2 mmol dm ⁻³ from the viewpoint of increasing the adsorption rate.

  When contacting the adsorbent of the present invention with a solution containing at least one metal ion, the adsorption of the present invention with respect to 1 mmol of metal ions contained in the solution from the viewpoint of easily adsorbing the metal ions contained in the solution. The weight of the material is preferably 0.05 to 1 g, and more preferably 0.5 to 1 g.

  In order to selectively adsorb specific metal ions, it is preferable to adjust the pH of a solution containing at least one metal ion in advance. For example, from the viewpoint of easily adsorbing indium ions and / or gallium ions, it is preferable to adjust the pH of the solution containing at least one metal ion so that the pH at the time of adsorption equilibrium is 2 to 4. More preferably, the pH of the solution containing at least one metal ion is adjusted so that the pH at the adsorption equilibrium is 2 to 3, and the pH at the adsorption equilibrium is 2.5 to 3. More preferably, the pH of the solution is adjusted. For example, from the viewpoint of easily adsorbing indium ions and gallium ions simultaneously, it is preferable to adjust the pH of the solution containing at least one metal ion so that the pH at the time of adsorption equilibrium is 2 to 4. It is more preferable to adjust the pH of the solution containing at least one metal ion so that the pH at the adsorption equilibrium is 2 to 3, and the pH of the solution is adjusted to 2.5 to 3 at the adsorption equilibrium. More preferably, the pH is adjusted. The pH can be adjusted using an alkali such as ammonia, sodium hydroxide, potassium hydroxide or lithium hydroxide, or an acid such as nitric acid, sulfuric acid, hydrochloric acid or perchloric acid. It is more preferable to adjust the pH using nitric acid and sodium hydroxide because the generation of metal complex anions can be minimized.

  The adsorbent of the present invention is usually solid, and the adsorbent of the present invention that adsorbs metal ions is also usually solid. Therefore, after the metal ion-containing solution and the adsorbent of the present invention are brought into contact, solid-liquid separation is performed by, for example, filtration, and the adsorbent of the present invention that has adsorbed metal ions can be easily removed from the solution. it can. As a method for recovering metal ions from an adsorbent on which metal ions have been adsorbed, for example, an adsorbent on which metal ions have been adsorbed and an acidic solution or a basic solution are brought into contact with each other, so that the metal ions are removed from the adsorbent into the solution. And a method of incinerating an adsorbent on which metal ions are adsorbed and recovering metal ions. The adsorbent can be regenerated and the metal ions can be further separated by selecting an acidic solution and a basic solution, so that the adsorbent is brought into contact with the acidic solution or the basic solution to desorb the metal ions. The method is preferably used.

The present invention further includes a step of bringing a solution containing at least one metal ion into contact with the adsorbent of the present invention; and an adsorbent adsorbed with the metal ion obtained in the step, an acidic solution or a basic Contacting the solution to desorb the metal ions from the adsorbent;
A method for recovering metal ions is provided.

  Regarding the step of bringing the metal ion-containing solution into contact with the adsorbent of the present invention in the recovery method of the present invention, the above description relating to the adsorption method of the present invention also applies.

  In the recovery method of the present invention, by contacting the adsorbent of the present invention adsorbing metal ions with an acidic solution or a basic solution, the metal ions are desorbed from the adsorbent into the solution, and the metal ions are recycled. It can be recovered in a possible state. Furthermore, according to the recovery method of the present invention, the adsorbent can be regenerated.

Although it does not specifically limit as an acidic solution, The solution of inorganic acids, such as hydrochloric acid, a sulfuric acid, nitric acid, phosphoric acid, or organic acids, such as an acetic acid, a citric acid, and an oxalic acid, is mentioned. From the viewpoint of application to industrial waste liquid or leachate, it is preferable to use an aqueous hydrochloric acid solution as the acidic solution. The amount of the acid varies depending on the type of the acid and the like, but from the viewpoint of facilitating waste liquid treatment, it is preferably about 1 to 3 moles relative to the metal ions to be eliminated. The concentration of the acid is not particularly limited vary depending on the type of acid, for example, in the case of hydrochloric acid solution, from the viewpoint of efficiency of concentrating and recovering, preferably 0.1 to 2 mol / dm ^3, more preferably 0 0.1-1 mol / dm ³ . Since the adsorbent of the present invention can desorb metal ions using an acidic solution having a relatively low concentration, the treatment of the waste liquid after the desorption treatment is easier.

Although it does not specifically limit as a basic solution, For example, the aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia is mentioned. Since selective desorption of gallium ions from the adsorbent of the present invention adsorbing metal ions is facilitated, it is preferable to use an aqueous sodium hydroxide solution as the basic solution. The amount of the base varies depending on the type of the base, but is preferably about 1 to 3 moles relative to the metal ion to be desorbed from the viewpoint of high desorption efficiency. Further, the concentration of the base varies depending on the type of the base and the like and is not particularly limited. For example, in the case of an aqueous sodium hydroxide solution, preferably from 0.1 to 2 mol / dm ³ , more preferably from the viewpoint of high desorption efficiency. 0.1 to 1 mol / dm ³ . Since the adsorbent of the present invention can desorb metal ions using a basic solution having a relatively low concentration, the treatment of the waste liquid after the desorption treatment is easier.

  The recovery method of the present invention may include one desorption step or may include two or more desorption steps. For example, after the first desorption step, the adsorbent is removed by filtration, and the desorption rate is increased by performing the second and subsequent desorption steps using the same or different acid solution or basic solution as the first time. be able to. Further, for example, by using two or more kinds of solutions having different pHs in two or more steps, the metal ions adsorbed on the adsorbent of the present invention can be desorbed stepwise and separated and recovered. .

In one embodiment of the present invention, indium ions and gallium ions are adsorbed on the adsorbent of the present invention by bringing a solution containing at least indium ions and gallium ions into contact with the adsorbent of the present invention. Next, the adsorbent adsorbing indium ions and gallium ions is removed from the solution by filtration or the like. The extracted adsorbent is preferably brought into contact with an acidic solution having a pH of 1 or less, more preferably 0.1 to 2 mol / dm ³ , and still more preferably 0.1 to 1 mol / dm ³ hydrochloric acid aqueous solution. Both indium ions and gallium ions can be desorbed from the adsorbent and recovered.

  In another embodiment of the present invention, indium ions and gallium ions are adsorbed on the adsorbent of the present invention by bringing a solution containing at least indium ions and gallium ions into contact with the adsorbent of the present invention. Next, the adsorbent adsorbing indium ions and gallium ions is removed from the solution by filtration or the like. When the adsorbed material taken out is preferably brought into contact with a basic solution, more preferably an aqueous sodium hydroxide solution, the gallium ions can be mainly desorbed from the adsorbent and recovered. Next, by bringing the adsorbent into contact with an acidic solution, indium ions and optionally remaining gallium ions can be desorbed and recovered from the adsorbent. According to this aspect, indium ions and gallium ions can be separated.

  In another embodiment of the present invention, the solution containing at least indium ions, gallium ions and zinc ions and the adsorbent of the present invention are preferably 2-4, more preferably 2-3, and still more preferably 2. Contact at a pH of 5-3. According to this aspect, indium ions and gallium ions are adsorbed on the adsorbent of the present invention, but zinc ions are not adsorbed. Then, by removing the adsorbent adsorbing the indium ions and gallium ions from the solution by filtration or the like and desorbing the metal ions in the same manner, the indium ions, gallium ions and zinc ions can be separated. This embodiment can be particularly advantageous in separating indium and gallium from byproducts such as residues in zinc refining.

  The respective metal ions recovered by the recovery method of the present invention may be further separated, concentrated and recovered by appropriately combining with known methods.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, these examples are for explaining the present invention and do not limit the present invention in any way.

[Preparation of cross-linked chitosan derivative introduced with citric acid]
Example 1
200 cm ³ of a 0.6 mol dm ⁻³ citric acid solution was added to 30.3 g of Kimikachitosan, stirred for 30 minutes, and placed in a petri dish. The obtained solution was dried under reduced pressure at 50 ° C. for 24 hours and then directly dried under reduced pressure at 120 ° C. for 90 minutes. Thereafter, it was dried at room temperature for 24 hours, dried under reduced pressure at 50 ° C. for about 15 hours, and then dried under reduced pressure at 120 ° C. for about 3 hours. The obtained reaction product was further dried at room temperature, immersed in hot water and allowed to stand, and suction filtration was performed. The reaction product was washed with hot water and then dried. The dried reaction product, chitosan citrate, is finely pulverized, and the pulverized product is washed with hot water, 1N-NaOH, 1N-HCl, distilled water, ethanol in this order using suction filtration, dried, and brown Of cross-linked chitosan citrate was obtained. A synthesis scheme of chitosan citrate is shown below.

[Adsorption amount and adsorption rate]
Example 2
Using the crosslinked chitosan derivative described in Example 1 as an adsorbent, the adsorption amount and adsorption rate were measured by the following methods.
Each pH of In (III), Ga (III), and Zn (II) contained at a metal ion concentration of 1 mmol dm ⁻³ and adjusted with ammonia and nitric acid (pH 1 to Table 3) An ammonium nitrate solution having a pH _ini ) was obtained. The solution thus obtained was weighed 15 cm ^{3 at a} time, added to a sample tube containing 0.05 g of an adsorbent, and shaken in a 30 ° C. constant temperature bath at a shaking speed of 120 rpm for 24 hours. Thereafter, the solution was filtered, and the pH (pH _eq ) of the filtrate was measured using a pH meter. The metal ion concentration in the solution before and after shaking was measured using an atomic absorption photometer (Hitachi Model z-2310, manufactured by Hitachi High-Technologies Corporation) and an IPC emission spectrometer (SHIMADZU ICPS = 7000, manufactured by Shimadzu Corporation). It measured using. For In (III) and Ga (III), a diluted solution obtained by diluting the solution 6 times with purified water was used. For Zn (II), a diluted solution obtained by diluting the solution 101 times with purified water was used. The metal ion concentration was measured and converted to the metal ion concentration of the solution before dilution. From the obtained metal ion concentration, the adsorption rate (%) and the adsorption amount (mmol / g) were calculated according to the following formula. In the formula, _Cini is the initial metal ion concentration (mmol dm ⁻³ ), and represents the metal ion concentration in the solution before adsorption. In this embodiment, C _ini is 1. C _eq is the equilibrium metal ion concentration (mmol dm ⁻³ ), and represents the metal ion concentration in the filtrate after the metal ions are adsorbed on the adsorbent. w is the weight of the adsorbent, and in this example w = 0.05 g.

The results obtained for indium ions, gallium ions and zinc ions are shown in the following Tables 1 to 3, respectively. FIG. 1 shows the relationship between the adsorption rate of each adsorbent of the present invention for each metal and the pH after adsorption equilibrium.

比較例１の吸着材は、０．１２ｍｍｏｌ／ｇのインジウムに対する吸着量を有し、０．０５８〜０．２０４ｍｍｏｌ／ｇのガリウムに対する吸着量を有していた。また、図２に、本発明によらない比較例１の吸着材の各金属に対する吸着率と吸着平衡後のｐＨとの関係を示す。 Comparative Example 1
The amount of adsorption and the adsorption rate were measured in the same manner as in Example 2 except that chitosan diglycolate represented by the following formula was used as the adsorbent.

The adsorbent of Comparative Example 1 had an adsorption amount for indium of 0.12 mmol / g and an adsorption amount for gallium of 0.058 to 0.204 mmol / g. FIG. 2 shows the relationship between the adsorption rate for each metal of the adsorbent of Comparative Example 1 not according to the present invention and the pH after adsorption equilibrium.

  As is clear from FIGS. 1 and 2, the adsorbent of the present invention has sufficient adsorptivity to each metal ion in the solution shown in Example 2, whereas the adsorbent of Comparative Example 1 has the same It does not have sufficient adsorptivity for metal ions. Moreover, when using the adsorbent of Comparative Example 1, it cannot be said that indium ions, gallium ions and zinc ions can be easily separated.

Example 3
Measurement of adsorption amount and adsorption rate in the same manner as in Example 2 except that metal ions of Pb (II) were used instead of metal ions such as In (III), Ga (III) and Zn (II). Went. For measurement of the metal ion concentration, a diluted solution obtained by diluting the solution 15 times with purified water was used.

The results obtained for lead ions are shown in Table 4 below. Moreover, in FIG. 3, the relationship between the adsorption rate with respect to the lead ion of the adsorbent of this invention and pH after adsorption equilibrium is shown.

Example 4
Measurement of adsorption amount and adsorption rate in the same manner as in Example 2 except that a metal ion of Co (II) was used instead of a metal ion such as In (III), Ga (III) and Zn (II). Went. For measurement of the metal ion concentration, a diluted solution obtained by diluting the solution 21 times with purified water was used.

The results obtained for cobalt ions are shown in Table 5 below. FIG. 3 shows the relationship between the adsorption rate of the adsorbent of the present invention for cobalt ions and the pH after adsorption equilibrium.

Example 5
Measurement of adsorption amount and adsorption rate in the same manner as in Example 2 except that metal ions of Mn (II) were used instead of metal ions such as In (III), Ga (III) and Zn (II). Went. For measurement of the metal ion concentration, a diluted solution obtained by diluting the solution 51 times with purified water was used.

The results obtained for manganese ions are shown in Table 6 below. FIG. 3 shows the relationship between the adsorption rate of the adsorbent of the present invention for manganese ions and the pH after adsorption equilibrium.

Example 6
Measurement of adsorption amount and adsorption rate in the same manner as in Example 2 except that metal ions of Mg (II) were used instead of metal ions such as In (III), Ga (III) and Zn (II). Went. For measurement of the metal ion concentration, a diluted solution obtained by diluting the solution 81 times with purified water was used.

The results obtained for magnesium ions are shown in Table 7 below. FIG. 3 shows the relationship between the adsorption rate of the adsorbent of the present invention for magnesium ions and the pH after adsorption equilibrium.

Example 7
Measurement of adsorption amount and adsorption rate in the same manner as in Example 2 except that metal ions of Ni (II) were used instead of metal ions such as In (III), Ga (III) and Zn (II). Went. For measurement of the metal ion concentration, a diluted solution obtained by diluting the solution 21 times with purified water was used.

The results obtained for nickel ions are shown in Table 8 below. FIG. 3 shows the relationship between the adsorption rate of the adsorbent of the present invention with respect to nickel ions and the pH after adsorption equilibrium.

[Adsorption isotherm]
In order to measure the saturated adsorption amounts of In (III) and Ga (III) by the adsorbent of the present invention, adsorption isotherms were measured. First, the initial concentration of In (III) and Ga (III) was adjusted to 15 cm ^{3 of} 0.1N hydrochloric acid solution adjusted so as to be 3 × 10 ^{−3 to} 20 × 10 ⁻³ mol dm ⁻³ , respectively. 0.05 g of the adsorbent of the invention was added, and the mixture was shaken in a constant temperature bath at 30 ° C. at a shaking speed of 120 rpm for 24 hours. After reaching equilibrium, the equilibrium metal ion concentration (C _eq ) was measured. The adsorption isotherm was applied to the Langmuir type for consideration. The Langmuir adsorption isotherm is shown in the following formula (1). Langmuir plot based on the following equation obtained by modifying it (2) adsorption equilibrium constant than the slope and intercept of (the horizontal axis _{C eq,} the longitudinal axis _{C eq} / q the plotted _{^{graph) K ad (dm 3 mmol -1}} ) And the saturated adsorption amount q _m (mmol g ⁻¹ ). In addition, in following formula (1) and (2), q represents the adsorption amount of a metal ion.

The saturated adsorption amount q _{m was} determined from the slope of the straight line represented by this equation, and the adsorption equilibrium constant K _ad was determined from the intercept. The results obtained for each of In (III) and Ga (III) are shown in Table 9 below.

  From the above results, it can be seen that the adsorbent of the present invention has a high saturated adsorption amount with respect to indium ions and gallium ions.

[Desorption rate]
Example 9
No. 2 in Table 1 of Example 2 The adsorbent adsorbed with indium ions collected by filtration in No. 2 was used for measuring the desorption rate. No. 2 in Table 2 of Example 2 The adsorbent adsorbed with gallium ions collected by filtration in No. 2 was used for measuring the desorption rate. HCl aqueous 0.1 mol ^{dm -3} or 1.0 mol ^{dm -3} concentration as desorbing agent, or with aqueous NaOH 0.1 mol ^{dm -3} or 1.0 mol ^{dm -3} concentration. 15 ml of the desorbing agent was added to each sample tube containing 0.05 g / 15 ml of each adsorbent collected by filtration, and the mixture was shaken at a shaking speed of 120 rpm in a thermostatic bath at 30 ° C. for 24 hours. Thereafter, the solution was filtered, and the metal ion concentration in the filtrate (hereinafter also referred to as “desorbed liquid”) was measured in the same manner as described above. From the obtained metal ion concentration, the desorption rate (%) was calculated according to the following formula. In the formula, C _ini and C _eq are defined in the same manner as described above. C _des is the metal ion concentration (mmol dm ⁻³ ) in the desorbed liquid.

The results obtained are shown in Table 10 below.

  From the above results, it is understood that indium ions and gallium ions can be desorbed simultaneously by using an acidic solution. Moreover, it turns out that a gallium ion can be mainly mainly selectively eliminated by using a basic solution. Moreover, since the adsorbent of the present invention can desorb metal ions even when a relatively low concentration acidic solution or basic solution is used, metal ions can be recovered more easily and efficiently. In addition, the waste liquid treatment of the desorbed liquid is easy.

Claims (6)

Formula (I):

An adsorbent comprising a crosslinked chitosan derivative containing a structural unit represented by:   The adsorbent for adsorbing metal ions according to claim 1, wherein the metal ions are at least one selected from the group consisting of indium ions and gallium ions.   A method for producing a crosslinked chitosan derivative containing a structural unit represented by the above formula (I), wherein chitosan and citric acid are mixed and subjected to a dehydration reaction under heating to simultaneously perform crosslinking and introduction of a functional group.   A method for adsorbing metal ions, comprising a step of bringing a solution containing at least one metal ion into contact with the adsorbent according to claim 1. A step of bringing a solution containing at least one metal ion into contact with the adsorbent according to claim 1; and an adsorbent adsorbed with the metal ion obtained in the step, and an acidic solution or a basic solution. And desorbing the metal ions from the adsorbent;
A method for recovering metal ions. A step of bringing a solution containing indium ions and gallium ions into contact with the adsorbent according to claim 1;
Contacting the adsorbent adsorbed with indium ions and gallium ions obtained in the step with a basic solution to desorb gallium ions from the adsorbent; and contacting the adsorbent with an acidic solution The recovery method according to claim 5, further comprising a step of desorbing indium ions from the adsorbent.

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